BAGHDAD — A Navy SEAL was killed Tuesday in an attack by Islamic State fighters in northern Iraq, highlighting the evolving nature of the Pentagon’s mission in Iraq and how American troops are serving closer than ever to the front lines.

The SEAL was identified as Charlie Keating IV, a former Phoenix high school star distance runner and the grandson of the late Arizona financier involved in the 1980s savings and loan scandal, according to the Associated Press.

Keating was killed when Islamic State fighters north of Mosul penetrated a front line of Kurdish peshmerga forces by about three miles, a U.S. military official said.

Keating was the third U.S. service member killed in combat since the military campaign against the Islamic State began in June 2014.

A Kurdish official said the death occurred after Islamic State fighters began attacking peshmerga lines at dawn near the town of Telskuf, about 20 miles north of Mosul, the Islamic State’s main stronghold in Iraq.

The attack involved “truck bombs supported by infantry,” the official added, an indication that common conventional Islamic State tactics were likely used.

U.S. Army Special Operations troops operate across peshmerga front lines, often spending hours at outposts gathering information about the Islamic State’s activity.

The small detachments, however, are usually stationed a few miles from the front to help coordinate airstrikes between peshmerga fighters and the joint command centers in Baghdad and Irbil, the administrative center of the semiautonomous Kurdish region in northern Iraq.